OP0241 BONE MICROARCHITECTURE ASSESSED BY HIGH-RESOLUTION PERIPHERAL QUANTITATIVE COMPUTED TOMOGRAPHY (HR-pQCT) PREDICTS FRACTURE RISK IN PATIENTS WITH RHEUMATIC DISEASES ON GLUCOCORTICOIDS
Authors: H. So, S. L. Lau, V. W. Hung, H. T. Pang, S. K. Y. Ying, K. Kwok, J. M. Lee, J. J. W. Lee, J. F. Griffith, L. Qin, L. S. Tam
Journal: Annals of the Rheumatic Diseases (2022)

Background Peripheral bone micro-architectural parameters assessed by high-resolution peripheral quantitative computer tomography (HR-pQCT) were able to discriminate vertebral fracture in patients with rheumatic diseases on glucocorticoid (GC) independent of areal bone mineral density aBMD. Whether these parameters could predict future fracture remained to be determined. Objectives The aim of this study was to compare the differences in baseline vBMD, bone microarchitecture and estimated bone strength in these patients with and without incident fragility fracture over a period of 5 years. Methods This was a multi-centered, retrospective, case-controlled study. Patients with rheumatic diseases on long term GC from 7 regional hospitals who had dual-energy X-ray absorptiometry (DXA) and HR-pQCT done were invited to have a 5th year follow-up assessment. X-rays were repeated. The occurrence of new fragility fracture after 5 years was documented. The baseline clinical characteristics, aBMD, FRAX and HR-pQCT parameters in patients who experienced a new fragility fracture during the 5-year follow-up period (incident fracture group) were compared with patients who did not experience a fragility fracture (control group). Results A total of 140 patients were recruited. The mean age of the patients, who were mostly female (80.7%), was 58.7 ± 12.5 years at baseline. SLE and RA were the commonest diagnoses. At baseline, 45.0% and 28.6% of the patients had osteopenia or osteoporosis respectively. The baseline 10-year major osteoporotic and hip fracture risks by FRAX were 13.3% and 6.0% respectively. After 5 years, 47 (33.6%) of the patients developed new fractures. The baseline clinical characteristics of incident facture group and the control group are shown in Table 1. Patients with incident fracture were older. They also had more prevalent fracture and worse mobility. The aBMD and FRAX scores were significantly higher in the incident fracture group. When comparing the HR-pQCT parameters, the incident fracture group had significantly worse vBMD, microarchitecture and bone strength particularly over the tibia at baseline. However, the changes in these parameters were not different between the 2 groups. Multivariate regression confirmed that the baseline vBMD, microarchitectural parameters and estimated bone strength over distal tibia were independent predictors of new fractures after adjusting for age, gender as well as baseline fracture, mobility and osteoporosis status. Table 1. Demographic and clinical characteristics at baseline Control groupn=93 Incident fracture groupn=47 p Age (years) 57 ± 12 62 ± 12 0.015 Gender, n (%) Female 74 (79.6%) 39 (83%) 0.629 Disease type SLE 40 (43.5%) 21 (44.7%) 0.711 RA 19 (20.7%) 12 (25.5%) Others 33 (35.9%) 14 (29.8%) Mobility class, n (%) Ambulatory 82 (88.2%) 34 (72.3%) 0.046 Stick-walking 9 (9.7%) 12 (25.5%) Chair-bound 2 (2.2%) 1 (2.1%) Previous fracture, n (%) 10 (10.8%) 12 (25.5%) 0.023 Medications Cumulative prednisolone dose (g) 20.4 ± 18.7 22.0 ± 15.5 0.604 Ever or current anti-osteoporotic treatment, n (%) 15 (16.1%) 11 (23.4%) 0.310 aBMD (g/cm 2 ) at Femoral neck 0.66 ± 0.12 0.60 ± 0.12 0.009 Lumbar spine 0.86 ± 0.15 0.80 ± 0.16 0.025 FRAX score (%) Major osteoporotic fracture 9.9 ± 9.4 20.6 ± 17.3 &lt;0.001 Hip fracture 3.7 ± 5.6 10.8 ± 13.2 0.001 HR-pQCT parameters* Distal radius:mTb.vBMD 82.0 ± 45.2 62.6 ± 42.4 0.016 Distal tibia: Average vBMD 258 ± 70 225 ± 70 0.010 Tb. vBMD 144 ± 42 122 ± 40 0.003 pTb. vBMD 221 ± 52 197 ± 46 0.010 mTb.vBMD 91.3 ± 37.7 70.0 ± 40.0 0.002 Tb. number 1.50 ± 0.28 1.36 ± 0.34 0.010 Stiffness 162139 ± 42623 142054 ± 35375 0.004 Est. failure load -8173 ± 2083 -7200 ± 1744 0.004 *Only statististically significant parameters are shown Conclusion A significant proportion (33.6%) of patients with rheumatic diseases on long-term GC developed new fragility fracture in 5 years, which could be predicted by the worse vBMD, microarchitecture and bone strength over tibia at baseline on HR-pQCT independent of aBMD. Disclosure of Interests None declared